Aerospace Materials & Fatigue

Subtopic: Composite Materials & Laminate Theory

For a homogeneous, isotropic material, the relation between the shear modulus ($G$), Young's modulus ($E$), and Poisson's ratio ($\nu$) is:

Subtopic: Composite Materials & Laminate Theory

The three-dimensional stress-strain relationship for an isotropic material is given as { $\sigma$xx $\sigma$yy $\sigma$zz $\tau$yz $\tau$xz $\tau$xy} = [ P Q Q Q P Q Q Q P 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 R 0 0 0 R 0 0 0 R] { 𝜀xx 𝜀yy 𝜀zz $\gamma$yz $\gamma$xz $\gamma$xy} where, $P, Q$ and $R$ are the three elastic constants, $\sigma$ and $\tau$ represent normal and shear stresses and 𝜀 and $\gamma$ represent normal and engineering shear strains. Which one of the following options is correct?

Subtopic: Composite Materials & Laminate Theory

Which of the following options is/are correct?

Subtopic: Composite Materials & Laminate Theory

The figure shows plots of two yield loci for an isotropic material, where $\sigma$I and $\sigma$II are the principal stresses, and $\sigma$Y is the yield stress in uniaxial tension. Which of the following statements is/are correct?

Subtopic: Fatigue Crack Growth & S-N Curves

It is desired to estimate the aerodynamic drag, D, on a car traveling at a speed of 30 m/s. A one-third scale model of the car is tested in a wind -tunnel following the principles of dynamic similarity. The drag on the scaled model is measured to be Dm. The ratio D/Dm is _________ (rounded off to 1 decimal place).

Subtopic: Composite Materials & Laminate Theory

Two cantilever beams (Beam 1 and Beam 2) are made of the same homogeneous isotropic material and have identical length $L$. Beam 1 has a solid circular cross-section of radius $R$, while Beam 2 has a hollow circular cross-section with outer radius $R$ and inner radius $R/2$. If identical tip loads $P$ are applied, the ratio of the tip deflection of Beam 2 to that of Beam 1 ($\delta_2 / \delta_1$) is:

Subtopic: Aluminum, Titanium & Aerospace Alloys

A cantilever beam having a rectangular cross-section of width 60 mm and depth 100 mm, is made of aluminum alloy. The material mechanical properties are: Young's modulus, E = 73 GPa and ultimate stress, $\sigma$u = 480 MPa. Assuming a factor of safety of 4, the maximum bending moment (in kN-m) that can be applied on the beam is _____ (accurate to one decimal place).

Subtopic: Aluminum, Titanium & Aerospace Alloys

A cantilever beam having a rectangular cross-section of width 60 mm and depth 100 mm, is made of aluminum alloy. The material mechanical properties are: Young’s modulus, $E = 73$ GPa and ultimate bending stress, $\sigma_{ult} = 300$ MPa. The maximum bending moment (in kN-m) that can be applied to the beam without failure is _________ (accurate to one decimal place).

Subtopic: Composite Materials & Laminate Theory

The total number of material constants that are necessary and sufficient to describe the three dimensional Hooke's law for an isotropic material is ____.

Subtopic: Composite Materials & Laminate Theory

A bar made of linear elastic isotropic material is fixed at one end and subjected to an axial force of 1 kN at the other end. The cross-sectional area of the bar is 100 mm 2, length is 100 mm and the Young's Modulus is 1105 N/mm2. The strain energy stored in the bar is ____ Nmm.

Subtopic: Composite Materials & Laminate Theory

It is desired to measure the Young's modulus and the Poisson's ratio of a given homogeneous, isotropic material. A bar of length 20cm and square cross-section (10mm× 10mm) of this material is subjected to a tensile load of 40kN. Under this load, length increases to 20.1cm while the cross- section reduces to 9.98mm× 9.98mm. Young's modulus and Poisson's ratio of the material are:

Subtopic: Fatigue Crack Growth & S-N Curves

Three identical eagles of wing span s are flying side by side in a straight line with no gap between their wing tips. Assume a single horse shoe vortex model (of equal strength $\Gamma$) for each bird. The net downwash experienced by the middle bird is

Subtopic: Composite Materials & Laminate Theory

A composite circular shaft is comprised of a steel core surrounded by an aluminum annulus, perfectly bonded to each other as shown in the fi gure. If it subjected to a pure torque, which one of the following statements is TRUE?

Subtopic: Fatigue Crack Growth & S-N Curves

If $|-2X + 9| = 3$, then the possible value of $|-X| - X^2$ would be:

Subtopic: Fatigue Crack Growth & S-N Curves

All professors are researchers Some scientists are professors Which of the given conclusions is logically valid and is inferred from the above arguments:

Subtopic: Fatigue Crack Growth & S-N Curves

An aircraft has an approach speed of 144 kmph with a descent angle of 6.6 o. If the aircraft load factor is 1.2 and constant deceleration at touch down is 0.25 g ( g = 9.81 m/s^2), its total landing distance approximately over a 15 m high obstacle is

Subtopic: Fatigue Crack Growth & S-N Curves

Two points (4, p) and (0, q) lie on a straight line having a slope of 3/4. The value of (p - q) is:

Subtopic: Fatigue Crack Growth & S-N Curves

In the early nineteenth century, theories of social evolution were inspired less by Biology than by the conviction of social scientists that there was a growing improvement in social institutions. Progress was taken for granted and social scientists attempted to discover its laws and phases. Which one of the following inferences may be drawn with the greatest accuracy from the above passage? Social scientists:

Subtopic: Fatigue Crack Growth & S-N Curves

Four archers P, Q, R and S try to hit a bull's eye during a tournament consisting of seven rounds. As illustrated in the figure below, a player recei ves 10 points for hitting the bulls' eye, 5 points for hitting within the inner circle and 1 point for hitting within the outer circle. AE Outer circle 1 point Inner circle 5 points Bull's eye 10 points The final scores received by the play ers during the tournament are listed in the table below. Round P Q R S 1 5 1 10 1 5 10 10 1 2 1 1 1 5 3 10 10 1 1 4 1 5 5 10 5 10 5 1 1 6 5 10 1 1 7 The most accurate and the most consistent players during the tournament are respectively

Subtopic: Fatigue Crack Growth & S-N Curves

It can be inferred from the passage that

Subtopic: Fatigue Crack Growth & S-N Curves

Which of the following statements is true for an aircraft flying at a low angle of attack?